Wallboard joint



July 21, 1936. PAGE 2,047,982

WALLBOARD JOINT Filed Sept. 15, 1934 I 20 21 Q C] l v.

INVENTOR JOHN I AQE- E 5 BY ATTORN E Patented July 21, 1936 PATENTOFFICE WALLBOARD JOINT John Page, Evanston, Ill., assignor to UnitedStates Gypsum Company, Chicago, 111., a corporation of Illinois"Application September 13, 1934, Serial No. 743,847

7 Claims.

This invention relates to building constructions and has reference moreparticularly to wallboard joints and their method of preparation.

In the history of the building industry, various proposals have beenmade for treating the joints of wallboards when attached to studs withtheir edges abutting. One of these joint treatments is covered in patentto Green No. 1,703,667, in which a perforated metal tape is adhesivelysecured over the wallboard joint, the perforations being provided topermit drying out of the adhesive and also to somewhat improve the bondof the tape to the face of the boards. sulting joint is covered with aplastic paint, wall paper, or other decorative covering.

Cloth tapes and paper tapes have also been used. Cloth tapes have lowtransverse tensile strengths and high stretch so that they are apt torupture andpermit cracks to form in the decorative coatings. The same istrue of the paper tapes which have heretofore been used. In additionpaper tapes heretofore proposed have a high transverse and longitudinalexpansion on wetting so that wrinkling due to application of adhesiveprevents the tape from lying fiat on the surfaces of the wallboards andalso produces hair line cracks along the edges of .the tape as it driesand shrinks.

In order to obtain sufficient cross tensile strength to prevent crackingat joints with ordinary papers it is necessary to use a paper ofconsiderable thickness. This is unsatisfactory for two reasons. First,the thick tape makes a thick bulging joint which is diflicult if notimpossible to hide. Second, due to the excessive thickness and resultantstiffness ofthe tape it will not shrink down properly into depressionsin the joint as the adhesive dries out. This meansunbonded areas of tapeover these depressions which will during painting swell slightly andform blisters. When the paint dries these blisters will not entirelystraighten out and will remain as small lumps which will make the jointunsightly.

In my preferred method of application the joint is first filled flushwith the surface of the board, covering nail heads, and if necessarybuilding up low spots. After drying, the rough spots and lumps arelightly sanded off to form as even as possible a flat bed for the tape.Next,

The re-- a thick heavy bodied adhesive is applied-over the filled joint.The tape is then placed'over this and pressed down firmly into it. Theexcess adhesive is squeezed out by this pressure and is scraped off. Theadhesive is made heavy for two reasons. First, to have sufficient bodyto hold down the edge of the tape and prevent it from curling. Second,in squeezing the excess of the heavy bodied adhesive out from under thetape the adhesive flows and fills every crevice and depression in thesurface of the board, incompletely filled nail heads, etc. Then as theadhesive dries, due to its tackiness and body, it pulls the tape downinto these depressions and bonds it to the board over the entire area oftape. If this type of adhesive were not used, there would be a hollowspot behind the tape over each depression. Later when dampened by waterpaint, the tape over this area will swell and blister. This is exactlywhat happened in previous tape systems where a thin adhesive or anadhesive previously applied to the back of the tape was used.

After the adhesive has dried and pulled the tape down into thedepressions a finishing or feathering cement is used to fill up thesedepresg5 sions and feather off the edges of the tape. When dry thiscement is sanded down to give a smooth even surface which when properlypaintedor treated with other conventional decorative materials issubstantially invisible.

An object of this invention, therefore, is to provide an improved tapefor application over the joints of wallboards.

Another object of the invention is to provide an improved paper tape forjoint treatment which has a high modulus of elasticity, a low transverseand longitudinal expansion on wetting, a high transverse tensilestrength and freedom from edge cracking when applied in a wallconstruction. 40

Another object of the invention is to produce an improved method ofapplying paper tape to wallboard joints.

A further object of the invention is to provide an improved wallconstruction embodying my improved joint tape; also to improve jointtapes and wallboard joints in other respects hereinafter specified andclaimed.

Reference is to be had to the accompanying I I drawing forming modifiedform of the joint tape.

In preparing a wall, ceiling or partition, it is customary to-providestuds or joists ill to which wallboards II areattached by nails 12a. Thewallboards II are often made with a gypsum core l2 faced on both sideswith paper cover sheets l3 which are folded about the edges of the coreI! to form folds 14 forming protected edges. The wallboards Il may alsobe made of vegetable fibers, such as the wood fiber insulating boardswhich are well known to the art. The wallboards may which will produce ajoint having a transverse tensile strength substantially equal to'thatof the board itself so that no cracks will be formed in the coating IIat the joint due to expansion and contraction-of the board because ofchanges in temperature or warping of the studs II. Thismaybeaccomplished inpart by utilizing a paper made in a paper machinewhich accomplishes a crossing of a substantial proportion of the fibersof which the paper is composed. This imparts to the paper a'hightransverse tensile strength, a low stretch, a high' breaking load, and ahigh modulus of elasticity. The tape also has a low transverse andlongitudirial expansion on wetting so that it lies perfectly fiat on thewall surface during application and during the drying of the adhesive.My improved method of application of the tape also contributes insecuring the above results.

In order to show the comparative strength of my improved tape comparedto other tapes previously' used, the following data is given-:

Ratio lon- Ratio cross Cross tentensile Longitudk isha? TransverseThickness sile mo- Oross tenstrength n81 tensile strength stretchMaterial 0! mm dulus oi sllestrength 01mm, strength of m oi ta at was ais /s 1224..., or .Bzr .5

lbs/inch 1 .001 m. l -f fg cent thickness thickness Paper tape No. l -Q.0. 045 71, 000 24 5. 3 49 10.9 Paper tape No 2 0.005 50,000 5.0 56 11.2Paper tape No 3. 0. 007 39. 285 33 4. 7 81 ll. 5 Paper tape N o 4- 0.00570,000 6. 0 49 9. 8 Paper tape No 5. 0. 0145 129, 000 '60 4. 14 145 l0.0 Kraft wrapping paper- 0. 005 85, 000 27 5. 4 7. 0 Wallboard paper 0.021 57, 600 32 1. 5 105 5. 0 Improved paper tape.- 0.0095 185,000 60-816. 3-8. 4 144-110 15. 2-12. 2 Perforated metal tape- 0. 004 95 Clothtape No. 1------ 0.000 -49 Cloth tape No. 2 sized 0. 013 23 also be thewellknown paper pulp boards.

In the joint between the wallboards, I preferably apply a crack fillercement having about the following composition:

Pounds Casein 48 High calcium lime 22 Bor 10 Mica--- 100 Marble flour-820 This cement is smoothed oil level with the faces of the boards andallowed to dry.

An adhesive I 5 is then applied to the surface of the board over thejoint, this adhesive preferably having about the following formula:

Pounds Cas i 850 Bora 42 Trisodiumphosphatennl 102 Tribromophenol 6After the adhesive is dried, a decorative coating I8 is applied to theexposed surface of the boards completely concealing the joint, thisdecorative coating being paint, wall paper or the like.

It will be noted from the above data that my improved paper tape ischaracterized by low stretch at breaking load, high modulus ofelasticity, and high transverse and longitudinal strengths, which makeit ideal as a joint tape over wallboard joints. In this connection, Iconsider that a paper joint tape should have a cross tensile modulus ofelasticity of at least 100,000 lbs/111.

My improved tape is also noteworthy in its unusually low transverse andlongitudinal expansion on wetting. The following data on expan-.- sionafter a 2 min. immersion in water at 70 F.

- illustrates this point:

I Expansion T Expansion 1 acrosstape y Percent Percent Improved papertape 0.78 0.25 Paper tape No. 6-- 2. 34 0. 52 Paper tape No. 7.. 2.3 0.5Paper tape No. 8-- I 2.6 0.25

I consider that a paper tape should have a maximum transverse expansionon wetting of 1.5%

.and maximum longitudinal expansion of 0.5% in order to providesatisfactory application characteristics.

Of course, a high strength and low stretch at breaking load of thefinished joint and its resistance to rupture due to thermal expansionand contraction and warping of the studs, are essential, and in this myimproved joint system excels.

The following data shows the superiority of my joint system:

Stretch at Ultimate Joint breaking strength load Lbalinch ofjoint InchuImproved joint tape 99 0 Perforated metal tape 82 0 Cloth tape No. 1--.76 96 Cloth tape No. 7. 60 K:

The superior bond between the improved paper tape and the wallboardsispartly responsible for the superior strength of the resulting joint.

In addition to the advantages of the improved joint as above set forth,I have so formed the edges of the paper tape, that all cracking of thedecorative coating at the edges of the tape has been practicallyeliminated. In the form of tape shown in Figs. 1 and 3, the edges of thetape have been serrated to provide irregular saw tooth projections 20.These projections 20 distribute the load at the edges of the tape wheredanger of rupture between the tape and feathering cement or wall finishis greatest. In the form of tape shown in Fig. 4. the edges of the tapeare irregular by wavy projections 2| which may be formed by cutting ortearing. Tearing of the V edges can be accomplished by, saw tooth rollsinstead of the conventional roll and knife. In the form of tape shown inFig. 5, bevels 22 are formed on the edges of the tape which servetosecure a better adhesion between the edges of the tape and the faces ofthe wailboards, as well as permitting a i better feathering out of theoverlying cement and decorative coating to form a smooth and in visiblejoint. These edge treatments combined with other advantageouscharacteristics of the improved tape, provide a crackless and smoothjoint not heretofore obtained.

I would state in conclusion, that while the examples describedconstitute practical embodiments of my invention, I do not wish to limitmyself precisely to these details since manifestly, the same can beconsiderably varied without departing from the spirit of the inventionas defined in the appended claims.

Having thus described my invention, I claim as new and desire to secureby Letters Patent:-

1. A paper tape suitable for adhesive attachment to wallboard joints,comprising a strip of paper having a substantial proportion of crossedfibers extending transversely of said strip, the

longitudinal edge portions of said strip of paper being weaker than thecentral portions thereof to retard the formation of edge cracks alongsaid tape when applied to said wallboard joint.

2. In a wallboard construction, the combination with wallboard havingthe edges thereof attached to supporting framework-in substantiallyabutting relation to form a wallboard joint, of a strip of thin papertape adhered thereto having a large portion of its fibers extendingtransversely of said joint.

3. In a wallboard construction, the combination with wallboard havingthe edges thereof attached to supporting framework in substantiallyabutting relation to form a wallboard joint, of a strip of paper tapeadhered thereto in which a large proportion of the fibers extendstransversely of the tape and of the joint, the edge portions of the tapebeing weaker than the centre portions thereof. I 4. In a wallboardconstruction, the combination with wallboard having the edges thereofattached to supporting framework in substantially abutting relation toform a wallboard joint, of a strip of paper tape adhered thereto inwhich a large proportion of the fibers extends transversely of the tapeand of the joint, the edges of the tape being feathered so as to retardthe formation of edge cracks along the tape edges.

5. In a wallboard construction, the combina- 3c --tio n with wallboardhaving the edges thereof attached to supporting framework insubstantially abutting relation to form a wallboard joint, of a strip ofpaper tape adhered thereto in which a large proportion of the fibersextends. transversely of the tape and of the point, the edges of thetape being serrated so as to retard the formation of edge cracks alongthe tape edges.

6. In a wallboard construction, the combination with wallboard havingthe edges thereof attached to supporting framework in substantiallyabutting relation to form a wallboard-joint, of a strip of paper tapeadhered thereto in which a large proportion of the fibers extendstransversely of the tape and of the joint, the edges of which tape beingsufiiciently irregular to retard the formation of edge cracks along thetape edges, the tape having a. minimum cross tensile modulus ofelasticity of 100,000 pounds per square inch.

7. A wallboard construction as in claim 2 in which the tape is notsubstantially thicker than CERTIFICATE OF CORRECTION.

Patent No. 2,047,982. July 2 1956.

JOHN PAGE.

It is hereby certified that error appears in the printedspecificatio'n'of the above numbered patent requi-ringvcorrection asfollows: Page 3, second column, lihe 67, 'claim 5, for the word "point"read joint; and that the said Letters Patent shouldbe read with thiscorrection therein that the same may conform to the record of the casein the Patent Office.

Signed and sealed this 15th day of September, A. D. 1936.

Henry Van Are dale

